You need to test each line for the USA in the location, I personally would use the split function to create an array so that you know you are testing the location value and not finding the value at any location in the line that you have read using
ioLine = ioFile.ReadLine
while not ioLine = ""
ioLine = ioFile.ReadLine
dim Values as string() = ioLine.split(" ")
if not values(2) = "usa" then
iolines += system.environment.newline & ioline
end if
end while
Documentation on String.split:
String.split function[
^]